The field of the invention relates to high frequency welding of steel to copper, especially a steel terminal to a copper electrode of a semiconductor device.
Semiconductor power devices as well as other electrical devices (for example, stud mounted diodes) which have large copper electrodes are commonly provided with a steel terminal which is connected to the copper terminal and which extends outwardly for convenient connection to external connectors. The copper electrode commonly has a large area planar surface and the steel terminal is commonly a flat piece of steel with its end bent at a 90xc2x0 angle so that the bottom surface of the bent end can make surface to surface contact to the flat copper surface with the steel body (which may be tubular) extending perpendicularly away from the at contact surface. The confronting surfaces of the steel and copper members are then mechanically and electrically connected as by welding.
The welds which have been formed in the past do not have a uniform quality, and the weld is sometimes defective. This defect is frequently not detected until the semiconductor device has been fully assembled and is in operation in a circuit.
It would be very desirable to provide a weld process which makes a uniformly reliable weld of copper to steel.
A process for welding steel to copper comprises coating a surface of the copper with a thin flash of an alloy of silver and copper and high frequency welding the steel to the surface of the copper. An advantage of the process is that the weld between the steel and the copper has a uniform, high quality.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.